Have you built dry boxes like this one, or this one, or any of the other multitudes out there that use a cereal box like this? More importantly, did it come with a funnel? Especially a funnel with a roughly 20mm inner diameter hole on the small end?

Why bother drilling a hole into the cereal box that you can't plug, or printing an entire lid for the top, when you can just use that funnel to let your filament fly freely while keeping the spool as dry as a desert? Print this little cap out and you can let just the filament out nice and neat!

Why not just use the funnel on its own? …why ask these questions?

This funnel cap is designed to fit the cap of the narrow funnel that's typically used for pouring cereal that comes with a lot of the inexpensive plastic cereal boxes that are being used for filament dry boxes. It fits a standard PC4-M10 pneumatic connector if you want to hook a Bowden tube up to your dry box. The cap itself just slips over top of the funnel. The funnel is shaped in an unusual way, which means the cap will only fit on one way. Keep twisting when putting it on and it will eventually stay flat. If you want to guarantee an air-tight seal, you can use an O-Ring inside the cap, but I haven't tried this myself so let us know if it works for you.

For print settings, defaults will work fine. Heck, you could print it as flimsy as you like and it'll probably be fine. Maybe. Personally I like:

• .4 nozzle
• .2 layer height
• 3 wall loops
• Cubic infill, 15%
• No support, no brim, no raft, no fuss.

But honestly do whatever works best for you. Mine is printed in PLA Matte, but it should work in anything. Use TPU and you might get a proper airtight seal out of it. Maybe.

The STL is modeled in the “upright” orientation, that is, the orientation it will be attached to the funnel. You'll probably want to flip it in your slicer though. I just couldn't be bothered in Fusion.